What is the biological value of protein quality?

January 4, 2026 •

4 min read

The biological value (BV) of egg protein is traditionally considered the gold standard, often given a reference score of 100. This measure helps determine how efficiently your body can use the protein you consume from different food sources.

Quick Summary

This article explores the concept of biological value, a key measure of protein quality that assesses how efficiently dietary protein is absorbed and incorporated into body proteins. It covers the factors influencing BV, such as amino acid composition, compares BV with other protein quality measures, and explains how to improve overall protein utilization.

Key Points

BV Definition: Biological Value measures how efficiently the body uses absorbed protein for tissue formation.
Complete vs. Incomplete: Complete proteins (animal-based) have all essential amino acids and a higher BV, while incomplete ones (plant-based) are often deficient in some.
Limiting Amino Acid: The availability of the lowest essential amino acid determines the overall protein synthesis from a food source.
Protein Complementation: Vegetarians and vegans can achieve high-quality protein by combining different plant sources, such as rice and beans, to create a complete amino acid profile.
BV Limitations: BV is an older metric that doesn't account for digestibility and is measured under specific lab conditions, unlike newer methods like DIAAS.
Practical Application: For a balanced diet, consuming a variety of protein sources is more important than focusing solely on the BV of a single food.
Beyond BV: Other factors like digestibility, overall energy intake, and individual metabolic needs affect a protein's utilization.
Reference Value: Whole egg protein is historically used as the standard, with a biological value of 100, though some proteins like whey can achieve higher relative scores.

Understanding the Biological Value (BV) of Protein

Biological Value (BV) is a fundamental measure of a protein's quality, indicating the proportion of absorbed dietary protein that becomes incorporated into the body's own proteins. A higher BV signifies that a protein source provides essential amino acids in the right proportions for efficient protein synthesis, making it a crucial metric for athletes, individuals with specific dietary needs, and anyone looking to optimize their protein intake. While BV is a valuable tool, it's important to understand its nuances and limitations in the context of real-world dietary patterns.

How Biological Value is Measured

The calculation of Biological Value is based on nitrogen balance studies. Proteins are a primary source of nitrogen, and BV measures the amount of nitrogen retained by the body versus the amount absorbed from food. The formula for BV involves calculating the nitrogen used for tissue formation divided by the nitrogen absorbed from food, with the result multiplied by 100 to be expressed as a percentage of nitrogen utilized. Whole egg protein has historically been used as the standard reference, with a BV of 100, though some protein sources like whey can achieve a higher relative BV.

Factors Influencing a Protein's BV

Several factors determine the BV of a protein source, primarily its amino acid composition. Proteins are made from amino acid building blocks, and the body requires nine essential amino acids (EAAs) that it cannot synthesize on its own.

Amino Acid Profile: A protein source is considered 'complete' and has a higher BV if it contains all nine EAAs in sufficient amounts and proportions. Animal proteins, such as meat, dairy, and eggs, are typically complete proteins. Plant proteins are often 'incomplete,' lacking or being low in one or more EAAs.
Limiting Amino Acid: The EAA present in the lowest quantity relative to the body's needs is called the limiting amino acid. This single amino acid can effectively cap the rate of protein synthesis, regardless of how much of the other amino acids are present. For example, lysine is often the limiting amino acid in many plant proteins, while rice protein is low in lysine but rich in cysteine and methionine.
Food Processing: Methods like cooking and severe heat treatment can damage or destroy certain amino acids, reducing their availability and consequently lowering the protein's BV.
Mineral and Vitamin Content: The presence of certain vitamins and minerals is crucial for cellular function and the utilization of amino acids. A deficiency can negatively impact BV.

Comparing BV to Other Protein Quality Metrics

While BV is a useful metric, it has some limitations and other methods exist for evaluating protein quality. Each system offers a slightly different perspective on how effectively a protein is used by the body.


Feature	Biological Value (BV)	Protein Digestibility Corrected Amino Acid Score (PDCAAS)	Digestible Indispensable Amino Acid Score (DIAAS)
Measurement Basis	Nitrogen retention efficiency from absorbed protein.	Amino acid profile and fecal digestibility.	Amino acid profile and ileal digestibility.
Key Consideration	How efficiently absorbed protein is used for body protein synthesis.	Amino acid composition relative to human needs, corrected for digestibility.	Amino acid absorption in the small intestine, considered more accurate than PDCAAS.
Standard	Whole egg protein (historically, BV of 100).	A reference pattern of essential amino acids for preschool children.	An ideal amino acid reference pattern, often with different patterns for different age groups.
Limitations	Does not account for digestibility; measured at low intake levels, which may not reflect real-world diets.	Can potentially overestimate protein quality due to reliance on fecal digestibility.	More complex to measure but offers greater accuracy regarding true amino acid availability.
Common Use Case	Older, foundational metric still cited, particularly for comparing animal vs. plant proteins.	Common for labeling food products in some regions, though being phased out by some organizations.	The most current and recommended method by the Food and Agriculture Organization (FAO).

Can Plant-Based Proteins Have a High BV?

Yes, absolutely. While most animal proteins are complete and have a high BV on their own, a carefully planned vegetarian or vegan diet can combine various plant protein sources to achieve a high biological value. This practice is known as "protein complementation," where different plant foods lacking in certain essential amino acids are eaten together or over the course of a day to form a complete amino acid profile.

Complementary Protein Combinations:
- Rice and Beans: Rice is low in lysine, while beans are low in methionine. Eaten together, they form a complete protein.
- Peanut Butter on Whole Wheat Bread: The lysine in peanuts complements the methionine in wheat.
- Hummus and Pita Bread: The chickpeas are balanced by the wheat in the pita.

The Takeaway for Optimizing Your Protein Intake

Understanding what is the biological value of protein quality is just one piece of the nutritional puzzle. For most healthy individuals consuming a varied diet, focusing on obtaining all essential amino acids from a mix of sources throughout the day is more practical than fixating on the BV of a single food. However, for those with higher protein needs, such as athletes, or those on restrictive diets, being mindful of protein complementation and choosing higher BV sources can be beneficial for maximizing muscle repair and growth. Always consider factors like digestibility and overall dietary context, not just the isolated BV score.

Conclusion: Moving Beyond the Number

In conclusion, the biological value of protein quality offers a scientific way to assess how efficiently a single protein source can be utilized by the body. Proteins with a high BV, typically found in animal products, contain a complete profile of essential amino acids. However, smart combinations of plant-based proteins can easily compensate for their individual deficiencies, providing an equally high-quality protein intake. The emphasis should be on consuming a balanced and varied diet that meets all essential amino acid needs, rather than chasing the highest single BV score. For most, focusing on the diversity of protein sources will naturally ensure high-quality protein nutrition for optimal health and bodily function.

Frequently Asked Questions

A high biological value (BV) is generally considered to be a score of 70 or higher. Whole egg protein is used as a reference with a BV of 100, while other sources like whey protein can have a relative BV even higher than 100.

Animal proteins usually have a higher BV because they are complete proteins, meaning they contain all nine essential amino acids in the proportions needed by the human body. Plant proteins are often incomplete, lacking or having very low levels of one or more essential amino acids.

Yes. This process, known as protein complementation, involves combining different plant protein sources throughout the day. For example, combining rice (low in lysine) with beans (low in methionine) results in a complete protein with a higher BV.

Not necessarily. While a high BV indicates efficient amino acid utilization, a varied and balanced diet is most important. Other factors like digestibility, overall caloric intake, and the quality of your full meal also play a significant role in protein utilization.

BV measures how much absorbed protein is utilized, while PDCAAS (Protein Digestibility Corrected Amino Acid Score) and DIAAS (Digestible Indispensable Amino Acid Score) also factor in digestibility. DIAAS is considered the most modern and accurate measure, assessing amino acid absorption in the small intestine rather than the less precise fecal digestibility used by PDCAAS.

Yes, but it depends on the cooking method. While proper cooking can sometimes increase protein digestibility by breaking down structures, excessive heat treatment can denature proteins and destroy or alter essential amino acids, potentially lowering their BV.

Historically, whole egg protein is used as the standard with a BV of 100. However, relative to this standard, whey protein often scores higher, with reported values around 104, making it a very efficient protein source for the body.